


Promises we keep

by InkyOverlord



Category: Undertale (Video Game)
Genre: Ambiguous Relationships, Ambiguous/Open Ending, Blood and Injury, Emotional Hurt/Comfort, Emotional Manipulation, Implied Romance, M/M, Mild Fluff, Other, Vomiting, dream tried to be a good bro, slightly yandere?
Language: English
Status: Completed
Published: 2020-03-02
Updated: 2020-03-02
Packaged: 2021-02-27 21:54:09
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,591
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22982842
Author URL: https://archiveofourown.org/users/InkyOverlord/pseuds/InkyOverlord
Summary: promises can make or break someonebut they mean the world if no one else can understand what you go through
Relationships: Nightmare sans & Nightmare sans, nightmare sans/nightmare sans
Comments: 4
Kudos: 63





	Promises we keep

**Author's Note:**

> random idea i had at midnight: hey what if the scary Nightmare was some voice?
> 
> btw corrupted Nightmare is just Nightmare and pre-corrupted Nightmare is just called Nighty
> 
> and Nightmare talks in italics

If there was one thing about Dream,it’s that he knew about a lot of things,after all,he’s lived here longer than the village has.If a village had a question he’d definitely had an answer to it.

Though there was one question in his own mind that he couldn’t answer,no matter how he worded the question.

He was making his way up to the tree like no other day,his boots leaving marks of squashed grass since the grass has grown up to the lighter guardian’s knees.As per usual,he attempts to greet his brother but stops himself as he began to hear murmurs behind the tree,a worried look his across his face as he peers around the trunk of the tree to see his brother face away from him,sitting down,talking about something,making vague gestures in the air.

“Nighty?” He calls out,startling the darker guardian.

Nighty quickly turns to face his brother with a bright smile,as if what happened earlier didn’t exist,”Ah hello brother,I see your early”

“I thought I’d stop by real quick,just to check up on you” he explained,”who were you talking to just about now?”

“A-Ah no one!” Nighty quickly stutters out,quickly standing up,”I was just talking to myself hehe”

The lighter guardian couldn’t help but look at his brother in worry,at first he really did believe that Nighty was just talking to himself but after he heard some of the things he was saying,it was almost as if he was talking to someone—perhaps it was just an imaginary friend to help ease his loneliness though it didn’t really explain why Nighty keeps on denying he does it.

But Dream decided to leave him be and not pester him too much,”alright then,I’ll just head back to the village”

“Okay! Have a safe trip!” He replied with a smile.

Dream could only smile back though it was traced with slight worry but nevertheless he headed back to the village.Nighty watched on as his brother disappeared out of his sights.

_ Dream is quite the nosy one _

The voice echoed inside his skull,it drip with a vile raspy tone,enough to startle a person.

But not Nighty.

“He’s just looking out for me Nightmare” He replied towards the empty space.

Nightmare seemed to scoff,

_ I can look out for you just fine _

Nighty rolled his eyes but didn’t reply to the voice.Nightmare had been around him for a long time and was really the only friend he had,of course he couldn’t really others for thinking that something was wrong with him,he used to think he was also going crazy as well but he grew a soft spot for the voice and tried to ignore what the villagers said about him.He remembers meeting Nightmare on a late night,he couldn’t help but cry out his heartache and frustrations into the cold wind—he couldn’t help but scream his non existent lungs out about how much he hates being alive and being tortured daily,deep down—he wished that someone could protect him from whatever life threw at him—and that’s when he met Nightmare.

_ I promise to protect you,after all you mean the world to me _

At first,he was startled from the deep voice–as well as embarrassed that someone heard him vent but over time he had grown accustomed to him—even giving him a name since he seemed to lack one.Despite their different personalities,he still appreciates Nightmare’s efforts.

“Say Nightmare,what do you think the weather gonna be today?” Nighty asked,glancing at the sky,seeing the clouds dance by.

_ See those dark clouds? A storm might be brewing _

Nighty furrowed his eyebrows worriedly,”oh,hopefully it’ll pass?”

_ Highly doubt it,it seems to be headed in our direction,we should seek shelter  _

“Shouldn’t the tree be enough?” He asked,patting on the bark of the tree.

_ For a slight drizzle maybe,however it looks like it might straight up down pour on us _

The darker guardian looked around his surrounding area,trying to think up some possibilities to hide.He turned towards the village that was down the hill,even though he considered an opinion to hide in the village but he knew that wasn’t an option in the first place.

_ You know they don’t accept you there _

Nightmare’s voice was filled with concern as Nighty looked away with a deep sigh,staring at the grass under him.

“I know” He said,”I don't blame them really”

_ Don’t say that! You are the kindest and smartest monster I've ever had the pleasure to meet,these mindless mortals don’t see how important you truly are. _

Nightmare sounded really out of breath,despite being only a voice.Nighty was slightly taken back from his outburst,he wasn’t really sure how to react--granted he couldn’t never take a compliment.Still,a smile curled up the darker skeleton’s lips,a soft glint of purple blush.

“Well,gosh i don’t know what to say Nightmare..” he manages to softly say out.

_ No need to,my dear moonlight _

His voice returns to a rough but soft spoken tone,though sadly it was swiftly cut short.

_ Speaking of mindless mortals,I suggest you duck right about now _

Nighty didn’t need to be told as he crouched down low just barely missing the rock that barely scraped his skull,the rock landed a few meters away as he stood up once more,turning his head to the direction of where the rock might’ve come from.

“Hey look who it is! The weirdo who talks to himself!”

He notices the group of teens,all of them are holding some sort of weapon,ranging from rocks to bats or rusty pipe,his knees locked up as his heels dug into the ground in fear,his body froze up like a deer in the headlights.The teens held their weapons up high as poor Nighty was parazyed with fear.

_ Nighty,run _

And so without a second thought,he bolted in the other direction,his mind running on pure terror,dirt was dug up from the ground from how hard his feet were hitting the ground.He could still hear them go after him,their voices fading in and out.

“Get him!” one of them shouts,followed by a few jeers and jabs from the other’s.

“N-Nightmare! What do i do!?!” Nighty exclaimed,his non existent lungs burn from his sharp inhales.

_ Go into the forest,they don’t know the woods like we do _

Nighty nodded as he committed to run,shadows of trees passed over head,sticks crunch under his boots as his legs were beginning to burn.He could still hear Nightmare’s voice,telling him where to go,which blocked a few of the teen’s harsh insults.He looks back to see that the teens were still chasing him at full speed,some begin to throw rocks that he thankfully dodged as he slipped and skidded against the dirt.

“They’re s-still following us!” He panicked,his breathing becoming heavy and fast.

_ Hide in the deeper parts of the forest,no mortal dared to go there and if they do,they certainly have a death wish. _

He nodded as he quickly shifted his direction to heads to the thicker parts of the woods,his soul was beating rapidly out of his chest as every part of his body was screaming as him to stop,throbbing painfully for a rest--but he couldn’t stop,he can’t stop---not now.Nighty dodges and weaves through the trees,he could still hear the teens but they’ve become a lot more distant.

As he ran further into the woods,more trees covered the sky,making the ground floor a lot more darker—of course making it harder to see for humans,he looked back once more when he noticed that the voices had disappeared,at first he was finally freed by pain for a brief moment—but he realized too late that he couldn't see in the dark either.

Before he could stop himself in time he tripped over a tree root that stuck out like a sore thumb and he was basically thrown down a deep,muddy,ditch.Once he hit the bottom of the ditch,scraping his head against a rock,Nighty cried out in pain and collapsed into a sobbing mess on the muddy ground,staining his vibrant purple uniform.

Every part of him was in burning agony,his head hurt,his lungs hurt,his legs hurt.All he could manage was a few hasty sobs as he screws his eyes shut to tried to ignore the rising pain in his body.Nightmare’s voice call to him once more,in a reassuring manner.

_ Nighty I need you to open your eyes _

“I c-can’t” he choked out,the darker guardian did try but a sudden rushing of a burning sensation stung his eyes.

_ I know you are in a lot of pain but I made a promise to help you,I can only do so much though,please open your eyes. _

After a few more pathetic sobs from the darker guardian,he slowly pushed himself off the ground,propping himself onto his knees,he winced as the sharp pain in legs from the shift of weight.Nighty swallowed a lump in his throat as he peeled his eyes open,tears still streaming down his cheeks,his blurry vision cleared up after a few stinging blinks as they focused on his new surroundings.

It was dark as Night in this part of the forest,only a few spots of light broke through and even then they never reached the forest floor before being swallowed up in the darkness itself.He managed to muster up enough energy to properly pull himself from off the floor,he couldn’t see much but he could only made him feel very on edge.

Nighty sniffled as he held onto his elbow,”what do we do now?”

_ We keep moving forward until we find a safer place to rest _

“But...it’s so dark” he replied anxiously.

_ I will help guide you,my vision is far more superior at night. _

“Oh I see..” Nighty murmured,as he took his first few steps into a direction,”So does that mean your blind during the day?”

_ Short-sighted to be correct _

Nighty nodded,”Well I’m lucky that I have you with me”

Nightmare didn’t respond other than a small hum as Nighty continued his trek along the forest floor,nothing particularly exciting thankfully was happening which gave them both some time to chat.

“If you had an actual body,what do you think it would look like?” Nighty asked,carefully moving his way around tree roots.

Nightmare sighed thoughtfully,Nighty could almost imagine him tapping his cheek in deep thought.

_ Probably would just look like you _

“Like me?” Nighty repeated,”how about something a bit more creative–go a bit wild!”

_ You know I’m not the creative type _

“At least try?  _ Pleaseeeee? _ ”

Nightmare let out a deep chuckle.

_ Alright alright–hmm maybe like one of a sea creature with those worms attached to it _

“You mean an octopus?” Nighty asked.

_ Ah yes those but a completely black one—with only one blue eye _

“Wow that’s actually pretty neat” he complimented as his boots splashed some puddles.

_ It’s really not much...but having a body would help protect you _

“But if you have a body you’ll be free to go wherever you please,why stay with me?” He asked once more,get a long pause from the voice.

_ Because I made a promise to protect you and I care about you _

Nighty breaks some twigs under his boots as he marched on forward,”but why me? Out of everyone in the village why did you choose me?”

  
  


_ Because your in pain Nighty _

He abruptly stopped in his tracks,a flood of emotions hits him hard.

_ Not just physical pain but mental pain,you may deny that there’s nothing wrong but deep down in your soul you’re wondering what did you do to deserve this? Why am I alive? Why bother trying? _

Nightmare’s voice trembles with every self deprecated question but he pressed on.

_ I know well that you wish you were dead,so that the pain would stop,so you would stop hearing them scream how worthless you are,Well I’m not gonna let you die,not here and not now _

Nighty doesn’t response—he’s trying not to avoid the flooding of tears once more.

_ You are more than your magic,I’ve seen part of you that I absolutely adore,your charm and kindness is something I’ve never seen in this world.You have potential my dear Nighty and I’m not letting it go to waste. _

Nightmare fell silent once more,waiting to see if the other skeleton had something to say.Nighty didn’t really respond as he marched forward toward the unknown,it left most of the trek a bit awkward now.

  
  


_ Nighty,up ahead _

His voice catches him off guard slightly but nevertheless he glances up to only be met with darkness.

“I don’t see anything” Nighty spoke.

_ Straight ahead there is a cave  _

“A cave?” Nighty repeats.

_ Yes,we can rest there for the time being,but be careful things may lurk in there. _

Nighty gulps harshly,”y-you’ll tell me if you see s-something right?”

_ Of course,I will not let my guard down,even for a second. _

With one sharp inhale,the darker guardian moves on forward into the care,pressing his hand against the cold stone walls to keep his guide up. Eventually he stopped and sat down,pressing his back against the wall as he curled his knees to his chest.

Nightmare could tell something was up with the other,if he had a body,it would be filled with worry—perhaps he had overstepped his boundaries with Nighty,perhaps admitting those things upset him?

_ Nighty what’s wrong? _

He lets out as heavy sigh,his chin against his knees,”just thinking about what you said”

So Nightmare was right.

_ What about it? _

“Im just..not use to hearing that” He admits,his gaze meets the floor,glancing over cracks,”I feel like a don’t deserve it”

_ But you do deserve it,you mean the world to me _

“I know but just to let you know,even when I say horrible things about myself,I still do appreciate you words” He replied,wiping his damp face slightly.

_ I’m glad,now rest Nighty,I will keep an eye out _

Nighty nods,fluttering his eyelids shut,”Hey Nightmare?”

_ Yes? _

“I’m glad your a part of my life” Nighty yawns,his voice trembles in exhaustion,”please don’t ever leave..”

And with that the darker guardian is out like a light,leaving the voice to himself.He made a small humming sound to ease the smaller one into a deeper sleep.

_ Don’t worry my dear Nighty,I have no plans on doing that ever _

**_I promise_ **

~

Nighty stirred slightly in his sleep as the sound of pitter-patter rang through his skull.He manages to crack his eyes open slightly only to be met with darkness,more darker than usual.

_ Goodmorning Nighty  _

Nighty whined slightly as he rubbed his eyes,”morning Nightmare,is it raining right now?”

_ It seems so,the storm passed us and you slept right through it _

“Well I suppose that’s a good thing” he yawned,slowly managing to stand up,”we should get back to Dream,he’s probably worried about me”

_ Like he cares,he probably didn’t even know you disappeared  _

“He cares” Nighty confronts,”Just in his own way”

Nightmare didn’t respond other than a small huff.

_ Regardless,it’s still raining so we might have to wait it out a bit _

Nighty agreed as he made his way to the entrance of the cave,watching the rain trickle down softly,splashing into puddles of various sizes.The darker guardian scrunched up his nose as a cold gust of air blew in,his bones slightly rattled when a shiver went down his spine.

_ The rain looks lovely  _

Nighty hummed As he continued to stare off into the distance as the two stayed there for the time being.

Eventually the clouds grew apart,only letting out a soft sprinkle of rain,a perfect time head off back the way they came.Climbing up the muddy ditch,leaving his knees stained with dirt and grass,mud from the recent rain clumped onto his violent boots,turning them to a murky purple.A few more instructions from Nightmare had finally lead them out of the deep ends of the forest.

Nighty stopped for a brief moment to finally allow himself to stretch,inhaling some good after-rain air.

“Nice to finally see the sun again” Nighty commented.

_ Indeed,however you look like a mess _

Nighty glanced down at his lower part of his body,attempting to shake off the dirt,”I guess your right,I hope I have spare pants back at home”

He continued his trek through the forest,occasionally some small comments or mindless chatter would occur between the two.It quickly died down once the break way of the trees was becoming visible,leading back to an opening field of grass.

“Oh we’re back!” Nighty exclaimed.

_ Thank the stars _

Nightmare’s voice seemed relieved but still dripped with a cautious tone,the risk of bumping into one of those troublesome villagers was quite low due to the setting sun as the clouds began to drift away from their home but the voice would rather not take that risk.As Nighty continued his trek to the tree,the cool breeze of the recent rain sent a slight shiver but left him in a much more content tone,once the view of the tree cane closer—he could just barely make out the shape of his brother.

He couldn’t help but move at a much more brisker pace,a sense of relief washed over him once his brother’s gaze was focused back on him.Nighty didn’t have any time to react before he was tackled by the lighter guardian,almost suffocating in his brother’s clothes—Dream’s grip was like iron bars and just wouldn’t budge.

“Oh thank the stars you're alright!” Dream cried out in joy,”I thought something horrible happened to you–and,and I thought you—“

Nighty managed to free himself from the other’s grip as he tried to explain himself,”I’m fine brother–really,I assure you—just had a run in with some villagers”

_ Run in is sure a nice way to put it _

Dream blinked in surprise,”really? Again? I’ll might have a word with the village chief if this keeps up”

Eventually the lighter guardian broke away from the embrace as Nighty quickly changed the topic of interest.

“Hey Dream,do we have any clean clothes?” He asks before gesturing to himself,”I kinda tripped into a puddle”

He hummed in thought before he walked past Nighty,straight towards the tree,”I think so? Let me quickly check”

The lighter guardian begins to climb up the tree,soon disappearing into the leaves as the apples danced about followed by more rustling from up above.

_ The only trait that I appreciate from your brother is that he isn’t nosy  _

“He really isn’t someone to seek that kind of thing”

_ But it makes him very naive  _

Nighty hummed slightly in response before taking his attention to the branches up above as his brother called his name.

“I have some spares but I hope you don’t mind some bland shirts” Dream calls out,”I’ll have to wash your uniform in the morning”

“That’s fine by me” He replied back,soon following his brother’s steps as he climbed up the tree as well.

Once he was up,Dream handed him some fresh set of clothes before climbing down to give his other half some privacy,the thick bushy leaves gave Nighty enough sense of security as he began to strip down off his clothes.As he did this he noticed how quiet Nightmare suddenly went,the sound of the rustling leaves were nothing compare to Nightmare’s deep growly voice.

“Nightmare?”

_ Yes? _

Nighty manages to set his pants to the side,slipping on the fresh ones,”you’ve been very quiet”

Apologies Nighty,I just wanted to give you some privacy

A bit of silence drags on,”a-are your eyes closed?”

It never occurred to Nighty that the voice might’ve been watching him undress during their time together,suddenly a small rush of embarrassment washes over him,a sense of self consciousness creeps up on him.

_ Well I don’t really have physical eyes,but yes all I’m seeing is pitch black _

He didn’t reply instantly as he began to unbutton his shirt,though he was hesitant on what to say next.

“Well….since we technically share the same body” His voice drifts off,”—um that,you can look,if you want to”

_ Are you sure? _

Nightmare asking that did make him slightly unsure but he shook his head,”I’m certain”

He soon sheds his shirt,exposing his slightly dirty bones,traces of scars that never seem to end.This sudden exposure and knowing that Nightmare was watching him was causing his poor cheeks to fluster up pretty badly.

Nightmare didn’t seem to respond as he grabbed the fresh top and began to dress himself,the shirt’s sleeve was slightly shorter compared to his usual clothes so it exposed some of his scars,even though Nightmare wasn’t talking—he knew he was watching,he could feel it.

Once he was done,he quietly cleared his throat,”N-Nightmare?”

_ Yes? _

“I’m done” He stammers out,tugging on the ends of his sleeves.

_ Very well,shall we head back down? _

Nighty nodded as he set old clothes to the side before heading back down,his shoes met the earth with a damp thump,most of the water from the recent rain had run off,leaving the ground a bit moist,nevertheless he sat down,his back firmly pressed against the tree.Clouds had left a while ago leaving a colorful array of the night sky.

He was left in awe,no matter how many times he’s seen the stars,they always left him breathless.

“Gorgeous aren’t they?” Nighty spoke quietly.

_ Indeed,they are _

The two fell back into silence,enjoying the site above them.

_ Nighty,I want to ask you something  _

“Hm?”

There was a slight delay in Nightmare’s response,

_ those scars...those mortals did that to you _

Nighty went quiet but he nodded softly.

_ I want to make another promise to you _

“Yes?” He asked

_ I promise from this day onwards that I will never let another mortal lay a finger on you in such a way _

Nighty didn’t understand what the other meant by that,his eyebrows furrowed in confusion—how could Nightmare ever do such a thing? He wasn’t physical,the best he could do was tell Nighty what to do.

He didn’t ask what the other meant however,assuming he meant to just keep an eye on him,”thanks Nightmare,I really appreciate”

_ Of course,now rest—it’s been a long day for you my dear Nighty _

Nighty agreed,letting out a soft yawn as curled up to his knees,”alright,goodnight Nightmare”

And with that he was out like a light.

~

This wasn’t supposed to happen

He didn’t mean to—it was an accident!

He couldn’t get it through the angry crowds,that continued to hiss and spit out absolute vile words at him—all those words had become so loud that it just became nothing but garble to him.

It was just a normal day like any other—except for the fact that he had touched one of his brother’s golden apples by accident,he didn’t mean to,he was just curious,the minute he touched it the whole tree went rot and dark clouds swirl above.

Through his tears he could see his brother trying to talk them down but they didn’t listen,many grabbed him by the shirt and began to scream at him.

This was too much,he wanted this to stop—all of this.His thoughts were to swarmed to critically think,his soul was beating violently out of his chest that he was beginning to shake badly,his breathing was so rapid that the air was burning his throat that he might just pass out from it.

He could only just press his hands to cover his ears over the violent yelling and screaming—he needed some one,anyone to help him from his suffering.

_ Nighty! _

A single voice had called,muting out all other voices,he looked up but he already knew how it was.

_ I need you to listen to me,see the tree? _

He was willing to do anything at this point,his throat was too raspy to reply back but he nodded.

_ Go to the tree _

He did as he was told,not even thinking about his brother,who was calling his name—only to be suffocated by every other voice.

At the trunk of the dying tree laid a single black apple,Nighty’s apples.

_ See that apple? _

“Y-yes” he replies in a raspy voice.

_ I need you to eat it _

“E-eat It?!” Nighty exclaimed,”but I don’t know what they’ll do to me!”

_ Nighty,do you trust me? _

He almost found himself hesitant on replying,”yes”

_ Then I promise you,this is the only way I can help you,please trust me _

Nighty picked up the corrupted fruit,gazing into its black reflection,he knew this was a dangerous thing to do,however the angry villagers were closing in on him—he had to act.

He pierced his teeth into the forbidden fruit,tasting a sweet,sinful bitterness before finally swallowing it.

“NO!” His brother screamed out in absolute horror.

Nighty suddenly felt his whole body go into shock,collapsing onto the ground as he began to cough and gag,his gut was gurgling and twisting as he felt a acidic bile began to rise up his throat.He soon screamed in absolute agony as a black sludgy goop escaped his mouth and stained the earth beneath him.

“It—it hurts!” He managed to cry out As more bile came out,burning his throat.

He couldn’t stop it,it continued to rush out of his mouth,he could barely breathe as he violently gagged and choked.

Soon his tears began to turn into the black goop,stinging his eyes,his vision was becoming spotty but he could still see the horror in each and every villagers face—including his brother’s face.

“P-please—m-make—it–it stop” He weakly croaked out,as he tried to reach out,but something was holding it down.

Suddenly he wasn’t moving,he couldn’t move.

“ _Rest easy my dear Nighty_ ” Nightmare’s voice spoke a soothing tone,except he realized something that his voice wasn’t coming from his head—but rather his own mouth.

“Nn—night..”He wanted to say some,but the air was getting thin and his eyes were growing heavy that he soon submitted to the darkness.

Nighty’s form was no longer,instead what became of him was a mass of goop that vigorously began to move and take form,it stood up,flexing off its many tentacles.

“ _Don’t worry Nighty_ ” He spoke,a singular cyan eye glowed threateningly.

“ ** _I promise to protect you_** ”

  
  
  
  
  
  



End file.
